<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>引出生命周期</title>
  <!-- 引入Vue -->
  <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>
  <!-- 准备好一个容器 -->
  <div id="root">
    <h2 v-if="a">你好啊</h2>
    <h2 :style="{opacity}">欢迎学习Vue</h2>

  </div>
</body>

<script type="text/javascript">

  new Vue({
    el: '#root',
    data: {
      a: false,
      opacity: 1
    },
    methods: {

    },
    //Vue完成模板的解析并把初始的真实DOM元素放入页面后（挂载完毕）调用mounted
    mounted() {
      console.log('mounted');
      setInterval(() => {
        this.opacity -= 0.01
        if (this.opacity <= 0) this.opacity = 1
      }, this)
    },
  })

  //通过外部的定时器实现(不推荐)
  /* setInterval(() => {
    vm.opacity -= 0.01
    if (vm.opacity <= 0) vm.opacity = 1
  }) */
</script>

</html>